Aqueous dispersions and process of making same



Patented Sept. 20, 1932 UNITED STATES PATENT FFEC LESTER KIBSGHBRAUN, OF LEGNIA NEW JERSEY AQUEOUS DI SPElR'SIONS AND PROCESS OlE MAKING SAME No Drawing.

cerned with aqueous dispersions of such sub-,

stances as are made by effecting the dispersing action with the aid of organic colloidal materials such as gelatine, tapioca flour, wheat flour, dextrine, starch, starchcontaining substances and the like: I

It has been found, for example, that certain colloids of this type may be satisfactory for use as dispersing agents in the production of bitumen-pitch type dispersions, providing the dispersing operation is carried on-in such manner that the dispersed particles are maintained as the dispersed phase throughout the dispersing action. Dispersions as thus produced are highly stable in the presence of acids, alkalis, powdered pigments, hydraulic cement, and the like, and such dispersions are also suspendable over long periods of time and possess other desirable properties.

One of the ob ects of the present invention is to provide a method in which thedispersing action with the aforesaid materials may be facilitated, and the resultant product improved as to fineness of. particle size,

body, and use of quantities of dis- P persion means. I

While the sifie of the dispersed particles resulting from t e dispersion of bitumen-pitch type materials with dispersing agents of the 1 type indicated, is suificiently fine for most' purposes, nevertheless, in some instances, a much fined degree of subdivision is desired,

and it accordingly another object of the present invention to provide methods whereby the above named colloids may be employed for producing dispersions in which i the particlesdisperse'd are of an exceedingly fine order of subdivision, as a result of which the finished product possesses a muchffiner 5 and longer body than is obtainable with such by a certain degree of tackiness. This tack- -of drying to a continuous non-tacky and sub- Application filed December 15, 1927. Serial No. 240,387.

dispersing agent when used without the improved treatment presently to be described.

One of the characteristics of dispersions made with certain of the above named colloids is that when such dispersions are employed as coatings and applied in the form of films, the removal of the water and the consequent coalescence of the dispersed particles results in a film which is characterized mess is in certain instances desirable as providin adhesive qualities which adapt the film or use as a bonding coat. Under other conditions of use, however, it is desirable that the dried water-f'r'eefilm of the dispersion be .free of tackiness and hence another: object of the present invention is to produce dispersions of this type in which the dispersed particles are niuch finer than are ordinarily attainable and which are capable stantially impermeable film.

The foregoing objects areachieved by treating the colloid used as the dis ersing agent, in the manner to be hereina er described in more detail.

In carr ing out the invention tapioca flour or any 0 the common forms of starch, as for example, corn starch, potato starch, or the like, may be employed as the dispersing agent. The substance to be dispersed may comprise any solid or semi-solid bitumen such as asphalt, either of the native or artificially repared variety, resins, pitches, rubber, or the like, all embraced in the term bitumenpitch type., Where the material to be dis-, persed is a solid or semi-solid bitumen it may be preferably heated so as to be brought to a fiuid= condition. The temperature at which the bitumen may be maintained during the process of dispersion may vary over a considerable range, depending upon the character of the bitumen. Where starch is selected as the dispersing agent, the same may be preferably conditioned by forming a swollen paste thereof in water.

In one mode of carrying out the invention, forexample, tapioca flour may be cooked into a pastewith abon tfithree (3) times its weight of hot water.

e concentration of the bituminous material, the particles being thereby dispersed and maintained in suspension in the aqueous phase. ing apparatus may be of a type provided 5 with agitating propellers, or it may be of any'other suitabletype. The dispersing apparatus may be preferably provided with any'suitable means, such as water jackets or the like for regulating he temperature of the mass being treated therein.

'It is preferable in conducting the process asa batch operation, to add the heat-liquefied bitumen to thefiour vpasteand to continue the addition of bitumen during the agitation of the mass until the desired amount of bitumen has been dispersed in the form of finely divided particles. I

I have found in'accordance with one phase of the present invention, that if the paste :0 of the organic colloidal material is treated with an acid or acidic salt, that the dispersing action is thereby facilitated so that the desired end product may be more readily produced. For this purpose I may add to a :5 starch paste, for example, acids such as hydrochloric, acetic or sulfuric, or such acldlc salt as potassium dichromate, aluminum sulfate, or the like. The amount of acidlc substance added should generally be suflicient to bring the hydrogen ion concentration of the starchy paste to a value of, say 4.0 to 5.0.

At this range the dispersion of the base is more readily accomplished than when using a paste made with untreated starch.

When producing dispersions of this type with pastes made, for example, with carbohydric colloids, such as starch or starch-containing materials in their untreated state, the mass being subjected to the agitating or dispersing action is preferably maintained in a pasty condition, but the mass should not be permitted to become so thick as to cause the formation of coarse grainy particles or the coalescence of the dispersed particles.

I have found, however, in accordance with another feature of the present invention, that if relatively small quantities of a tannincontaining material or material functioning 80 as does tannic acid in this respect is prescut, a very superior type of dispersion may be produced by virtue of the fact that the presence of saioLmaterial permits theprocess to be carried on under such conditions that .the

mass undergoing dispersion is maintained in The dispersing ac The dispersa relatively thick pasty condition. Under such conditions of operation the high internal viscosity of the thick mass assists the dispersing action materially so that the particle-s are dispersed in an exceedingly fine state of subdivision such as isnot attainable where the operation is carried on while the viscosity of the mass is maintained relatively thin. The dispersion as thus produced is not only finer as respects the size of the dispersed articles, but in most cases it is also more smoothly and heavily bodied than the dispersion madewith the untreated starch paste.

One typeof material which I have found suitable for this purpose is tannic acid and tannincontaining substances such as tannic extracts, as for example, quebracho. I

The tannin-containing or tannin-like ma terial may, if desired, be incorporated during the dispersing action, but better results, are had by mixing the tannic acid orjta'nnincontaining substance with the said colloid and carrying on the dispersion with this mixture. In the latter case, the tannin-containing material may" be preferably subjected, together with the dispersing agent, to the action of hot water, whereby to form thereof athick viscous paste.

I have found that very small quantities of the tannin when mixedwith starch are suf- P ficient to accomplish the purpose of the present invcntion. T he quantities of tannic acid may range from, say 1% by weight of the starch to 10%, more or less, by weight there-- of. Larger quantities are to be avoided be cause of the resultant tendency to harmfully afiect the dried film of the product. \Vhere it is desirable to eliminate the tackiness which usually characterizes the dried film of dispersions made with carbohydric colloids, this may be accomplished with larger amounts of tannic acid within the range given above.

As a specific embodiment of this invention, a mixture may be made of 10 parts of corn starch with .2 parts of tannic acid, the mixture being then formed into a plastic mass by boiling in 80-40 parts, more or less, of water. Thisplastic mixture may then be employed in the dispersion of Mexican asphalt of, 100 to 200 F. melting pointor other similar bituminous material, the operation being carried on in such manner that the bitumen is at all times retained as the dispersed phase. In this way it is possible to disperse asphalt of the character indicated in quantities ranging from 30 to 40 times by weight of the amount of starch and tannic acid in the plastic mixture comprising the dispersive media, the aqueous v content of the final product constituting about 35-40% more or less, thereof. The dispersion thus produced may, therefore,comprise, say 1.5 to 2.0% starch, 015% to 05% of tan nioacid, is substantially perfectly suspendable and very stable in the presence af alkalis,

acid salts, powdered pigments, mineral aggregate and the like, none of the latter causing any perceptible amount of flocculation of the dispersed particles or producing. any other objectionable effects in the dispersion.

Substantially similar results may be attained by substituting quebracho for the tannic acid. This extract contains compounds of tannin in amounts equivalent to about 35% of its weight of tannic acid, and hence where this material is available it may be used in substantially the manner above set forth, and in quantities such that the tannin content thereof approximates the quantities of tannic acid above specified. The product made with this material is substantially similar in all respects to the dispersion made as above described with tannic acid.

A dispersing agent such as gelatin also lends itself very well to the above treatment with tannins or tannic acid, in which case the gelatin becomes insolubilized so that it is irreversible in the final water-free film.

The product thus produced may be used a protective coating with or without pigments and fillers. It may be mixed with mineral aggregates and used as a road binder. Fibrous materials such as asbestos or Vegetable fibres may be incorporated readily with it to produce plastic fibrous com ositions capable of use for roofing or as a ase for mastic flooring mixtures.

Rust inhibitive agents, either soluble or insoluble in the aqueous phase may be readily incorporated into this dispersion without the occurrence of flocculation whereby to produce a coating readily adapted for protection of iron and steel.

By the term tannin-like substance as used in the claims I mean tannic acid, tannin extracts, and substances generally functioning in the same manner as do these substances when used with an emulsifying agent of the type referred to in the foregoing description.

I claim as my invention:

1. The herein described process of producing an aqueous bitumen-pitch type dispersion, which comprises making an aqueous paste of a carbohydric colloid, adjusting said paste to a pH va1ue of 4.0 to 5.0, by a tanninvlike substance and dispersing a bitumen-pitch type base with said adjusted paste.

2. An aqueous bitumen-pitch type dispersion comprising by weight at least substantially 60% of bitumen-pitch type base, 1.5% to 2% of a paste-forming carbohydric substance, 0.015% to 0.2% of a tannan-like substance, and the balance water.

3. An aqueous bitumen-pitch type dispersion comprising by weight at least substantially 60% of bitumen-pitch type base, 1.5% to 2% starch, 0.015% to 0.2% of a tannin-like substance, and the balance water.

In testimony whereof I affix my signature.

LESTER KIRSCHBRAUN. 

